Abstract

We report here the prevalence of parasitism by water mites (Arrenurus sp.) and terrestrial mites (Leptus killingtoni) on parthenogenetic Ischnura hastata (Odonata: Coenagrionidae) from the Azores islands. Leptus killingtoni was only found on the island of Pico, and the prevalence of infestation was highly variable among the different ponds studied, ranging from 0 to 41%. Leptus killingtoni was observed on three of the four odonate species from the archipelago: I. hastata, I. pumilio, and Sympetrum fonscolombii, all of them new hosts for this species. Aquatic mites have been found parasitizing I. hastata females on the island of São Miguel. The prevalence of mite parasitism by Arrenurus sp. on I. hastata was very low, ranging from 12% (2003) to 1% (2008), and in most of the studied ponds, no mites were found attached to females. Although I. hastata coexists with a sexual congener species in the Azores (I. pumilio), they are syntopic in only a small fraction of ponds. Therefore, a comparison between I. hastata and I. pumilio was insufficient to test the predictions of the Red Queen Hypothesis, and further research on parasitism rates in both species needs to be done. In any case, the low prevalence of mite parasitism found in the Azores, coupled with the fact that most of the populations in the archipelago are almost free from competitors and predators, could explain the persistence of these I. hastata parthenogenetic populations, despite their low levels of genetic variation.

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Acknowledgments

Funding was provided by the Spanish Ministry of Science and Innovation (grant CGL2005-00122, including FEDER funds, to ACR, and grant CGL2009-08943 to AGV). We thank the Instituto para a Conservaçao da Natureza (Lisbon) and the Secretaria Regional do Ambiente e do Mar (Faial Island, Azores) for permits to collect damselflies. Many thanks to all the people that helped during field work: Inés González de Castro and Kathleen Harding in the Azores; Laura Sirot in Florida; Alejandro Córdoba-Aguilar, Sandy Upson, Robert Behrstock and Doug Danforth in Mexico; Yusdiel Torres-Cambas and Adrián Trapero in Cuba; and Melissa Sánchez Herrera and Emilio Realpe in Colombia. A. Zawal and P. Martin kindly provided us with copies of their papers on arrenurid larvae. SEM analysis of mites was done with the help of Jesús Méndez and Inés Pazos from the “Centro de Apoio Científico e Tecnolóxico á Investigación” (CACTI, Universidade de Vigo).

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